Asthma is the most common cause of respiratory disability in children. One of the common factors associated with asthma fatality is failure to recognize the severity of the asthma attack. This project has demonstrated that children with a history of life threatening asthma attacks (LTA) have a significantly decreased perceptual sensitivity to increased extrinsic loads and an increased threshold for detection of an increased extrinsic load. The absence of an early component, the P1 peak, or the respiratory related evoked potential (RREP) is indicative that there may be an intrinsic neural processing deficit in some children with LTA. The studies performed to date in this project demonstrate that one component of the child's failure to recognize an asthmatic attack in its early stages may be a reduced perceptual sensitivity to an increased load. The primary goal of this project is to continue the investigation of the neurophysiologic and behavioral mechanisms which may be mediating this failure of some asthmatics to recognize the severity of their asthma. Specifically, the sensory processes mediating bronchoconstriction, respiratory load perception and subsequent behavioral responses in asthmatic children. These studies will test the hypothesis that the sensation of mechanical loads is related to the components of the RREP. It is further hypothesized that the late components of the RREP are correlated with cognitive processing of respiratory loads. The significance of the work lies in the fact that impaired perception of intrinsic and extrinsic loaded breathing may put some asthmatic patients at risk of underestimation of the severity of an attack, delay in awareness of onset, inadequate self-assessment and delay in seeking medical attention. The RREP is a unique measure of cortical neural activity elicited by breathing against a mechanical load. This technique will be used, in combination with established psychophysical measures, to test for differences in the neural processing of respiratory load information between LTA, non-LTA asthmatic and non-asthmatic children. The perceptual sensitivity and interaction of different types of stimuli will be investigated. An investigation of the relationship between neural measures of mechanical load afferent activation and subjective measures of load perception will be performed. Bronchoconstriction and resistive loads will be used to test for the correlation between intrinsic and extrinsic perception. The relationship between the component peaks of the RREP and respiratory loads will be determined. The cortical activation by loads will be measured and the RREP recorded with the inclusion and exclusion of the different mechanoreceptor populations. The results of this project will provide new information on the sensory mechanisms mediating respiratory sensation in LTA asthmatic and non-asthmatic children. These results will be used to develop a better physiological understanding of self-assessment mechanisms in these children and used to provide enhanced treatment.